Generally, robots have been used in various places of works of persons that are not safe, impossible or inefficient. In addition, conventional robots have been used in repetitive works, or works that require high-level accuracy to increase productivity and quality of products. The conventional robots have been developed for a variety of fields, such as for research, home use and crime prevention as well as various industrial fields. Therefore, recently, it is required that each of actuating units of the robots is operated within a wider range.
Mobile robots are representative examples of the conventional robots. In the conventional mobile robots, a plurality of devices, which really execute desired works, are provided on a turret which is placed on a support frame. By a rotation of the turret on the support frame, directions of the plurality of devices for works are determined.
For example, a mobile robot with a turret is disclosed in Korean Patent Registration NO. 322316 which was filed by the inventor of the present invention and has been registered. As shown in FIG. 4, in the conventional mobile robot disclosed in Korean Patent Registration NO. 322316, a plurality of wheels 206 are provided under a support frame of the robot to move the mobile robot. The plurality of wheels 206 are connected by first and second belts 201 and 202 to each other. The first belt 201 is wound around both a drive motor 204 and the wheels 206, so that the drive motor 204 rotates the wheels 206 through the first belt 201 to move the mobile robot. Both wheel cases which hold the wheels 206 and a turret shaft 205 are rotated by a steering motor 203 through the second belt 202 to determine a direction of the movement of the mobile robot. At this time, a direction of the turret is equal to the direction of the movement of the mobile robot.
However, in the conventional mobile robot disclosed in NO. 322316, to change the direction of the movement of the turret, the robot must be rotated while the second belt 202 is rotated by the operation of the steering motor 203. The above-mentioned movement of the robot requires excessive power consumption and limits the workspace of the robot.
Furthermore, when the turret is rotated at angles higher than a predetermined reference angle, the first and second belts, which connect the plurality of wheels to each other, and a plurality of wires, coupled between the support frame and the turret, may be undesirably entangled to each other. Thus, the conventional mobile robot disclosed in NO. 322316 is problematic in that the turret must be rotated within a limited angular range.
In an effort to prevent the plurality of wires of the conventional mobile robot from being undesirably entangled to each other while the turret is rotated, robot bases using slip rings were proposed in Korean Patent registration NO. 299622 and U.S. Pat. No. 4,657,104. The slip rings communicate powers and sensor signals between turrets and support frames, so that the robot bases have structures possible to endlessly rotate the turrets. However, the slip ring used in each of the conventional robot bases proposed in NO. 299622 and U.S. Pat. No. 4,657,104 causes undesired electric noise. Furthermore, it is very difficult to send high currents through the slip rings of the conventional robot bases. In addition, in case of using the slip rings for long periods, the slip rings must be worn. Because the slip rings are expensive, the conventional robot bases using the slip rings are problematic in that the production costs of the robot bases are increased.
In the meantime, a robot base having a structure possible to endlessly rotate a turret without any entanglement of wires is proposed in Korean Patent Application NO. 2002-0025612 which was filed by the inventor of the present invention. As shown in FIG. 5, the robot base disclosed in NO. 2002-0025612 includes a turret 308 and an electric part. The electric part is provided above the turret 308 and has a turret motor 301, a drive motor 303 and a steering motor 302. The robot base further includes a turret gear train 304 through which the turret 308 is rotated by an operation of the turret motor 301, and a drive gear train 306 through which wheels 307, provided under a support frame 309, are driven by an operation of the drive motor 303. The robot base further includes a steering gear train 305 to determine a direction of a movement of the robot base during an operation of the steering motor 302.
The turret gear train 304, the drive gear train 306 and the steering gear train 305 are arranged to form a triple shaft mechanism in that a drive shaft 311 of the drive gear train 306 is provided around a steering shaft 310 of the steering gear train 305. A turret rotating shaft 312 of the turret gear train 304 is provided around the drive shaft 311. The turret gear train 304 transmits a rotational force generated from the turret motor 301 to the turret 308. The drive gear train 306 and the steering gear train 305 transmit rotational forces generated from the drive motor 303 and the steering motor 302 to the wheels 307, respectively. As described above, the conventional robot base disclosed in NO. 2002-0025612 comprising the electric part at an upper portion of the turret 308 and a mechanical part at a lower portion of the turret 308 has a structure possible to endlessly rotate the turret 308 through the triple shaft mechanism.
However, in the conventional robot base disclosed in NO. 2002-0025612, the drive motor 303 and the steering motor 302 are rotated along with the turret 308 while the turret 308 is rotated by the operation of the turret motor 301. At this time, the drive motor 303 and the steering motor 302 are connected to the wheels 307 through the drive gear train 306 and the steering gear train 305, respectively. To prevent the above-mentioned changes in the locations of the drive motor 303 and the steering motor 302 from undesirably causing movements of the wheels 307, the drive motor 303 and the steering motor 302 must be appropriately operated in response to the rotation of the turret 308. Therefore, the conventional robot base disclosed in NO. 2002-0025612 is problematic in that its control algorithm is very complicated, and power consumption is undesirably increased.